The invention of the present application relates to an optically active fluorinated binaphthol derivative. More specifically, it relates to an optically active fluorinated binaphthol derivative, which is useful as an asymmetric catalyst or the like with excellent reaction yield and optical selectivity, an asymmetric metal catalyst using the same, and further, a method of asymmetric synthesis using this asymmetric metal catalyst.
Asymmetric synthesis has attracted much interest as a method of synthesizing organic compounds that are used in medical drugs or the like as biologically active substances. Optically active binaphthols have been known as substances constituting catalysts or reaction accelerators for such asymmetric synthesis.
For example, asymmetric metal complexes formed by the reaction of optically active binaphthols and metal compounds have been known.
However, for the optically active binaphthols proposed so far, such as halogen-substituted binaphthols, improvements of reaction yield and optical yield (selectivity) are not easy when used in asymmetric synthesis reaction, causing problems for practical use.
Accordingly, the invention of the present application aims to provide, upon solving the aforesaid problems of the prior technique, a novel optically active binaphthol derivative useful as an asymmetric catalyst or the like, with which higher reaction yield and higher optical yield (selectivity) may be attained in asymmetric synthesis reaction, an asymmetric catalyst using the same and a method of asymmetric synthesis.
As a solution of the above-mentioned problems, the invention of the present application first provides an optically active fluorinated binaphthol derivative represented by the following formula (I) 
(wherein R1 and R2 each represent a fluorinated hydrocarbon group), and secondly provides the optically active fluorinated binaphthol derivative, wherein the fluorinated hydrocarbon group of R1 and R2 is a perfluoroalkyl group.
Further, the invention of the present application thirdly provides a method for producing the optically active fluorinated binaphthol derivative of the first or second invention, comprising the substitution of halogen atom (X) of an optically active halogenated binaphthol derivative represented by the following formula (II) 
(wherein x represents a halogen atom, and R represents a protective group) with a fluorinated hydrocarbon group, and the elimination of the protective group (R).
The invention of the present application fourthly provides an asymmetric metal catalyst comprising the optically active fluorinated binaphthol derivative of the first or second invention and a metal, and fifthly, an asymmetric metal catalyst, wherein the metal is at least one element selected from the group consisting of boron, aluminum, titanium, zirconium, lanthanoid elements, gallium, bismuth, silicon and tin, is provided.
Further, the invention of the present application sixthly provides a method of asymmetric organic synthesis, comprising the formation of carbon-carbon bond using the asymmetric metal catalyst of the fourth or fifth invention.
The invention of the present application has the above-mentioned characteristics; hereinafter the embodiments thereof are described.
First, in the invention of the present application, the optically active fluorinated binaphthol derivative represented by the above-mentioned formula (I) is provided. In this derivative, symbols R1 and R2 in formula (I) are fluorinated hydrocarbon groups that refer to hydrocarbon groups with hydrogen atoms substituted with fluorine atoms. As the hydrocarbon groups, saturated or unsaturated aliphatic hydrocarbon groups are considered. The fluorinated hydrocarbon groups in the above-mentioned formula (I) of the invention are indicated to be these groups substituted with fluorine atoms. Specifically, perfluoroalkyl groups are preferable as the fluorinated hydrocarbon groups. Examples thereof include xe2x80x94CF3, xe2x80x94C2F5, xe2x80x94C2F3, xe2x80x94C3F7 and the like.
Such fluorinated hydrocarbon groups may be bound to various positions of a naphthalene ring of the binaphthol; typical examples would be those bound to the symmetric positions such as 6,6xe2x80x2- and 3,3xe2x80x2-.
Of course, in the optically active fluorinated binaphthol derivative of the invention, although not shown in the formula, substituents may also be bound to the naphthalene ring.
Further, the above-mentioned fluorinated hydrogen group is not limited to one on each naphthalene ring, but may be multiple groups bound to various positions of the naphthalene ring, as required.
The foregoing optically active fluorinated binaphthol derivative of the invention may be produced by the substitution of the halogenated binaphthol derivative represented by formula (II), as described previously.
To describe such method more specifically, for example, in the present invention, (R)-6,6xe2x80x2-(xcex1,xcex1,xcex1)-trifluoromethyl-2,2xe2x80x2-dihydroxy-1,1xe2x80x2-binaphthyl (compound 1) represented by the following formula 
is provided, which may be produced by the substitution of the halogen atom with a fluorinated hydrocarbon group as shown, for example, in the following reaction scheme. 
By the same process, for example, (R)-3,3xe2x80x2-(xcex1,xcex1,xcex1)-trifluoromethyl-2,2xe2x80x2-dihydroxy-1,1xe2x80x2-binaphthyl (compound 5) represented by the following formula 
may also be produced.
The optically active halogenated binaphthol derivative of the above-mentioned formula (II) may easily be prepared as a commercial product or by known processes. Further, needless to say, when the protective group (R) is unnecessary, a compound having xe2x80x94OH as such may be used as a starting material. The substitution reaction is not limited to the foregoing process, and various processes are available.
For example, in the process represented by the above-mentioned reaction scheme, a methoxymethyl group is used as the protective group (R). However, various groups may be used as this protective group. Further, the diiodo substitution product used as the starting material may be synthesized from the corresponding dibromobinaphthol. Detailed examples of the reaction are described in the Examples section.
For example, the optically active fluorinated binaphthol derivative of the present invention obtained by the foregoing method may be used effectively as the asymmetric auxiliary group or the asymmetric ligand in asymmetric synthesis. That is, asymmetric catalysts comprising the optically active fluorinated binaphthol derivative and metal are provided by the invention. In this case, the metal may be, for example, boron, aluminum, titanium zirconium, lanthanoid elements (scandium, ytterbium, lanthanum and the like), gallium, bismuth, silicon, tin and the like. These metallic elements may constitute the asymmetric metal catalyst by being mixed or reacted with the optically active fluorinated binaphthol derivative in a solvent in the form of halides, alkoxides, or complexes.
Such asymmetric catalyst may further contain an appropriate coordination compound or active compound. Examples thereof include amines, imidazoles, phosphines and the like.
Such asymmetric metal catalysts may be used effectively in asymmetric synthesis reaction by forming carbon-carbon bond through, for example, reactions such as aldol condensation, Diels-Alder reaction, alkylation, allylation or the like. The yield of asymmetric synthesis as well as the optical yield and the selectivity become extremely high.
Accordingly, Examples are demonstrated below to describe the embodiments of the present invention in more detail.